This invention relates to the delivery of excitation light to a target tissue and the collection of response light therefrom for spectral analysis.
Optical methods are being used with increasing frequency to determine the composition and state of samples. In particular, the use of optical techniques is growing in the medical arts for the diagnosis of tissue health in-vivo. In some instances, a beam of light is used to illuminate the tissue in a specific region, causing excitation of said tissue. Light emitted by the tissue is then collected by the receiving device and analyzed to determine the physical health of the tissue.
Two methods are known in the art that deliver and receive illumination from a designed region of tissue. In the first method, termed bistatic, the illuminating beam is focused on the sample from one direction, and light that is backscattered or emitted from the sample is received by an optical system located in a position different from the position of the delivery system. In the second method, termed monostatic, the illuminating beam path and the receiver beam path lie along the same line of sight. Such an optical scheme is also called confocal if the location of the sample is at the focal point of both the illumination optical system and the receiver optical system of the device.
According to the bistatic method for examining a sample, the field of illumination from the source and the field of view of the receiver are aligned so as to overlap at the sample, while illumination and viewing take place at different locations. Certain limitations are understood to accompany bistatic methods. For example, when this method is employed with an illuminating device that does not directly contact the sample, it is sensitive to misalignments of the device to the sample, so that any error in the distance of the non-contact device from the tissue may result in significant decrease in the amount of light collected by the receiver.
Bistatic optical probes may have illumination and receiving sections sufficiently separated from each other that the optical paths from the sample to each section are oriented along different directions. The effect of this optical design is that the illumination path and the receiving path form two sides of a triangle, intersecting in a single localized region. The surface of the sample may then be positioned in this overlap region. For some applications, this triangulation can be exploited. The receiver section may be configured to collect a signal only when the proper distance from the probe to the sample is achieved. In this embodiment, when the receiver section of the probe is detecting a signal, the distance from the probe to the sample can be known. This embodiment may lend itself to greater ease of analysis and probe calibration.
For many applications, however, the bistatic configuration is not useful. For example, contours to the sample may cause shadowing of the response from the surface of the sample to the receiver, or may cause the overlap of the receiver line of sight and the illumination line of sight to fall off of the surface. The monostatic optical design may overcome these problems. It is furthermore understood that misalignment problems can be overcome by use of a monostatic optical configuration. Additionally, if the monostatic optical configuration is also confocal, the optical receiver will collect only the light from the illuminated region on the sample.
In one embodiment of a monostatic device, the illuminating beam of light may be transmitted through a beamsplitter before it interacts with the sample. The light emitted by the sample returns to the beamsplitter, where it is reflected toward a receiver system in the device. If the illuminating excitation beam and the returned emission from the sample occupy different regions of the electromagnetic spectrum, the beamsplitter can be a dichroic mirror, with high transmission at the excitation wavelengths and high reflectivity at the sample emission wavelengths. This offers the possibility for high efficiency of optical throughput in the device. If, however, the spectral regions for the excitation and emission beams have significant overlap, the dichroic mirror cannot be used, and significant losses of optical signal can occur. In the case where the excitation and emission spectral regions are identical, the optimum beamsplitter will transmit only 50% of the excitation signal, and will reflect only 50% of the returned signal emitted by the sample. The overall efficiency of such a device is only 25%.
Another limitation of the use of a beamsplitter in the path of the excitation and emission beams is the possibility that light can be directly scattered from the illumination side to the receiver side of the probe without interaction with the sample. This can create large optical signals containing no information about the sample.
It is understood in the art that probes are available for multispectral imaging of a sample. A probe may comprise a housing and beam splitting apparatus within the housing, designed for imaging. Such a probe may not address the problem of scattering from the beam splitting surface and the level of interference this scatter will cause.
It is well known in the art that optical interrogation of samples may permanently alter the nature of the sample as a result of the measurement. Laser-induced fluorescence studies of samples, for example, temporarily alter the physical nature of the molecules in the sample. This alteration produces molecules in excited energy states that liberate optical radiation as they relax to the more favorable ground energy state. Chemical and biological changes in specific samples can also be created to liberate an optical response from the sample. An example of a permanent change in the sample is seen in laser breakdown spectroscopy, where a portion of the surface of the sample is ablated by the intense laser beam. The ablated material is in the form of an excited plasma that liberates light distinctive of the composition of the sample.
While some changes in the physical, chemical, or biological condition of the sample can be important for creating a response to the illumination, certain other changes in the sample that may be caused by an optical system or a probe may interfere with the desired measurement. For example, it is known from spectroscopic studies of in-vivo tissue that hemoglobin content can have diagnostic significance. Optical probes that contact the tissue can alter the flow of blood to the tissue, thereby altering the hemoglobin spectral feature. Such changes in sample characteristics adversely affect the ability of the optical device to measure the sample characteristics correctly. Contact of the probe with the target tissue may cause other relevant changes in the signals emitted from the tissue following illumination.
Probes in the art are known that identify tissue which is suspected of being physiologically changed as a result of pre-cancerous or cancerous activity by contacting the tissue, using separate optical fibers for transmitting the excitation light and receiving the emitted light, or using other conduits to direct heat, electrical, sound, or magnetic energy towards a target tissue. These devices rely upon contact with the tissues to derive their data, and do not embody a non-contact system for identifying tissue abnormalities.
Non-contact optical probes may be configured so they do not alter a sample in the same way as contact probes. Non-contact methods are particularly attractive in medical in-vivo diagnostic instrumentation because they do not perturb the tissue being investigated and because they do not carry the risk of contamination of the measurement site. However, non-contact probes can suffer from other limitations, most notably problems with alignment and focus. For proper operation, the two main components to the probe, namely the illumination section and the receiving section, must be aligned to the same location on the sample, and both must be in focus at the same time. Non-contact probes are known in the art that comprise systems for confocal illumination of a surface without including an apparatus for eliminating the scattered light from being transmitted from the transmitter portion to the receiver portion directly in the probe when a monostatic arrangement is used.
Therefore, there remains a need in the art for a confocal optical system that optimizes the retrieval of the emitted light from a sample after illumination in a monostatic configuration. There exists a further need to embody this system in a probe that does not require contact with the sample being illuminated. There exists an additional need for a non-contact probe that can measure the distance to the target tissue and that is adapted for optimal positioning with respect to the target tissue. No system exists presently in the art that permits an accurate non-contact technique of monostatic illumination of a sample without the potential of interference from scattered light from the components of the illumination probe. Additionally, when such optical probes are used in confined spaces, as is the case when illuminating in-vivo cervical tissue, the optical probe often obscures the common viewing of the tissue. Therefore, there is a further need to provide supplemental ability to view the target tissue during placement of the probe and during optical illumination.
It is desirable that an optical probe be provided for identifying light emission responses from a sample subjected to illumination. It is further desirable that the optical probe not interfere with physiological or morphological characteristics of the sample being examined, nor that the probe impede the ability of an optical system to detect identifying features of the response from the sample. If, for example, a desired response includes spectroscopic information (light intensity as a function of wavelength), the probe will advantageously be constructed so it will not contribute excessive spectroscopic detail to the signal. Similarly, if a desired response from the sample includes spatially related data, the optical probe will advantageously provide sufficient imaging quality to permit the identification of spatial components of the response.
In one embodiment, the present invention may comprise a probe bearing one or a plurality of lenses or mirrors for the purpose of bringing the illuminating light to a focus on the surface of the sample. The transmitting optics may occupy the center region of a cylindrical geometry. Surrounding the transmitter optics in this embodiment may be an annular optical arrangement for receiving emitted light from the sample. According to this embodiment, the emitted light returned to the probe passes through an optical system containing components different from the optical components used to form and direct the illuminating beam toward the sample, while remaining aligned to the same line of sight as the illuminating beam.
In one embodiment, the annular receiver optical system may be designed so that it accepts light emitted from the focused spot on the sample defined by the location of the illumination focal point. The emitted light from the sample collected by the probe receiver optics may then be brought to a focus elsewhere in the system for detection of for transport to a means of detection. This point of focus in the probe may be the active element of a detector, or may be the face of a fiber or fiber bundle, designed to conduct the light to another location in the device where the detection will take place. The terms receiving and collecting optics, as used herein, are understood to be interchangeable. Furthermore, the receiving optics are understood to collect, to receive and to retrieve light: all of the foregoing three terms are interchangeable, as they are used herein.
Because no single optical component is used in both the transmitter and the receiver portions of the device, the opportunity for scattered radiation from the illuminating source to enter the receiver portion of the device without first having interacted with the sample is greatly diminished, as compared to the technique of using a beamsplitter within the optical path. Care must be taken to account for light reflected from optical surfaces such as lens surfaces. This form of stray light can contaminate the measurement of the surface by passing directly from the illumination portion to the receiver portion of the probe without interacting with the sample. Practitioners of the art are familiar with baffles and stops to prevent this level of stray light contamination in the final signal.
In a particular embodiment, the sample being interrogated by the optical beam is in-vivo tissue. It is known in the art that when tissue is illuminated at a spatially limited point (e.g. 1-mm diameter spot) by a collimated beam of light, the emitted response from the tissue is in two parts. The first is a specular reflection from the surface, and is governed by Fresnel reflection created by the change in index of refraction between the air and the tissue. The second is a diffused reflection caused by the entrance of the light into the tissue where it migrates randomly before escaping the surface. It is known that this diffused reflection can occur over a wide angle from the surface. In some cases, this diffused component is modeled as having equal amounts of light in all angles measured from the perpendicular to the surface.
When the placement of the probe is critical to the quality of the measurement, and when the use of the probe is in confined spaces such as is the case when viewing in-vivo cervical tissue, it is useful to augment the operator""s viewing ability of the target. This may be accomplished by means of a video camera mounted directly in the probe. The optical system for the direction and focus of the illuminating beam can also serve as the optical system to create an image of the surface of the sample for the video camera.
In one aspect, the present invention provides a system for examining a sample that includes an optical probe with a plurality of optical fibers capable of illuminating a sample, and a substantially monostatic, substantially confocal optical system comprising transmitting optics to illuminate a sample and receiving optics to collect light emitted from the sample. In certain embodiments, the system may include a reflective optical component or a refractive optical components. The system may further comprise an optical system that focuses illuminating light on a surface of the sample and that collects light emitted from the focus point. In one embodiment, the receiving optics of the system may be configured circumferentially around a light path followed by the illuminating light. In one embodiment, the system may provide a scanner that directs illuminating light towards the sample by sequentially illuminating individual optical fibers in a preselected pattern, such as a rectilinear array or a hexagonal pattern. The illuminating light may include a pulsed laser or a nitrogen laser and the emitted light may include fluorescence or Raman scattered light. The illuminating light may include broadband light, for example from a Xenon lamp, and the emitted light may include elastic backscattered light.
In one aspect, the present invention provides a system for determining a characteristic of a sample that includes an optical probe for monostatic, confocal examination of the sample; an optics system that includes transmitting optics to focus an illuminating light on the sample and receiving optics to collect light emitted from the sample; a measuring system that produces quantitative data related to the light emitted from the sample; and a processor that processes the quantitative data to determine the characteristic of the sample. The system may further include a video system to display an image of the surface of the sample. The system may further include a position sensor to determine the position of the optical probe in relation to the sample. The position sensor may provide a focusing image that is projected upon a surface of the sample, whereby the position of the optical probe in relation is determined by the clarity of focus of the focusing image.
In another aspect, the present invention provides an optical probe system for the monostatic, confocal examination of a sample, including an optical probe, a light source that produces an illuminating light, transmitting optics that focus the light on a sample, collecting optics arranged substantially as an annulus surrounding a light path for the illuminating light that collect light emitted from the sample, and a connecting circuit that transmits electromagnetic energy related to the emitted light to a processor for further processing. The system may include a scanning system that sequentially illuminates a plurality of optical fibers to pass a point of illumination over the surface of the sample in a preselected pattern. The system may further include a video channel for viewing the surface of the sample and for determining the location of the probe relative to the sample. The video channel may share an optical path with the illuminating light. The system may include a video camera dimensionally adapted for mounting on an optical probe.
In another aspect, the present invention provides a method for examining a sample, including the steps of providing a monostatic, confocal optical probe with transmitting optics and collecting optics wherein the collecting optics are disposed around a circumference of a light path for transmitting an illuminating light towards the sample; determining an optimal position for the probe in relation to the sample and placing the probe in that position; illuminating the sample with a light beam transmitted through the transmitting optics; and collecting light emitted from the sample as a result of the illumination. The method may include the step of processing electromagnetic energy related to the collected light to derive data related thereto. The method may further include creating a graphic image to represent the data related to the light collected. The method may include directing a focusing image towards the sample to determine the optimal position of the probe in relation to the sample.
In another aspect, the present invention provides a method for diagnosing a medical condition, comprising the steps of providing a monostatic, confocal optical probe comprising transmitting optics and collecting optics wherein the collecting optics are disposed around a circumference of a light path for transmitting an illuminating light toward a body tissue; illuminating the body tissue; collecting light emitted from the body tissue; measuring a set of data related to the light collected from the body tissue; and diagnosing from the set of data the medical condition. The method may further include processing the set of data with a processor. The method may further include creating a graphical image that represents the set of data.
In another aspect, the present invention provides a method of treating a medical condition, including the steps of providing a monostatic, confocal optical probe capable of illuminating a body tissue and capable of collecting therefrom emitted light, illuminating the body tissue, collecting emitted light from the body tissue, measuring a set of data related to the light emitted from the body tissue, diagnosing from the set of data the medical condition, formulating a treatment plan based on a diagnosis of the medical condition, and treating the medical condition according to the treatment plan.
In another aspect, the present invention provides a system for examining a body tissue, including an optical probe that directs an illuminating light towards the body tissue and that collects light emitted from the body tissue; a substantially monostatic, substantially confocal optical system comprising transmitting optics that focus the illuminating light on the body tissue and receiving optics that collect light emitted from the body tissue; and a measuring system that produces quantitative data related to the light emitted from the body tissue. In one embodiment, the body tissue is the cervix uteri.
In another aspect, the present invention provides a system for evaluating a medical condition in a patient, including an optical probe that directs an illuminating light towards a body tissue and that collects light emitted from the body tissue; a substantially monostatic, substantially confocal optical system comprising transmitting optics that focus the illuminating light on the body tissue and receiving optics that collect light emitted from the body tissue; a measuring system that produces quantitative data related to the light emitted from the body tissue; a processor for processing quantitative data to derive diagnostic data related to the medical condition of the patient; and a database wherein the diagnostic data related to the medical condition of the patient may be stored. In one embodiment, the database may also store the patient""s medical record. In another embodiment, the system may include a tracker to record procedure data from the procedure wherein the system is used to evaluate the medical condition of the patient. The tracker may store procedure data in the database. The database may further comprise billing information, and the system may further relate billing information to the procedure data.
In another aspect, the present invention provides a method for delivering a health care service, including the steps of storing a medical record of a patient in a database; collecting billing information related to the patient; evaluating a body tissue of the patient with an optical system comprising an optical probe for monostatic, confocal examination of the body tissue using an illuminating light focused on the body tissue by transmitting optics and using a collection system for retrieving light emitted by the body tissue after illumination; processing the light emitted by the body tissue to produce a diagnosis of a medical condition of the patient; entering the diagnosis in the medical record; and relating the diagnosis to the billing information to generate a bill. The method may further include the step of recording procedure data in the database for the procedure of evaluating the body tissue. The method may further include the step of relating the procedure data to the billing information to generate a second bill for the health care service.
These and other features of the systems and methods of the present invention will become more readily apparent to those skilled in the art from the following detailed description of certain illustrative or preferred embodiments thereof.